FAS-Compatible Synthetic Signals for Equivalent-Linear Site Response Analyses

2018 ◽  
Vol 34 (1) ◽  
pp. 377-396 ◽  
Author(s):  
Margarita Chi-Miranda ◽  
Luis A. Montejo
Keyword(s):  
Site Response ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Extreme Value Statistics ◽  
Current Time ◽  
Equivalent Linear ◽  
Inelastic Demand ◽  
Design Response Spectrum ◽  
The Time Domain ◽  
Fourier Amplitude Spectrum

An alternative approach to generate the seismic input for equivalent-linear (EQL) site response analyses is proposed. The proposed approach encompasses the strengths from current time histories (THs) and random vibration theory (RVT) methods. It consists of the generation of synthetic signals in the time domain (analogous to the TH method) that are constructed to have a Fourier amplitude spectrum (FAS) compatible with the design response spectrum (analogous to the RVT method). Through this approach, the use of extreme value statistics (used in RVT and known to overestimate amplification functions) is avoided. Moreover, the need to develop an appropriate suite of realistic acceleration series, which is the most challenging and time-consuming part of the TH-based approach, is also circumvented. The methodology is evaluated through a comprehensive analysis that includes different site conditions, input spectral shapes, duration scenarios, levels of inelastic demand, and number of synthetic signals used.

The Research of Input Ground Motion on Seismic Fragility Analysis of Bridges

2012 ◽  
Vol 490-495 ◽  
pp. 1826-1830
Author(s):  
Yun Zhang ◽  
Pin Tan ◽  
Xiao Rong Zhou
Keyword(s):  
Ground Motion ◽  
Seismic Wave ◽  
Seismic Waves ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Design Response Spectrum ◽  
Methods Of Synthesis ◽  
Fourier Amplitude Spectrum

Analyzed the importance of selecting reasonably ground motion input in seismic fragility analysis of the bridge. Based on the common methods of synthesis artificial seismic wave which used trigonometric series and according to the characters of Fourier series, extracted phase spectrum from practical seismic waves ,through modulating the Fourier amplitude spectrum, obtained the artificial seismic wave which fitted compatible with the design response spectrum. Similar to nature small earthquake records, it has the character of non-stationary on time-domain and frequency-domain. Synthesize a series of artificial seismic waves in this method, can improve the accuracy and pertinence of the bridge seismic fragility.

scholarly journals Detecting Site Resonant Frequency Using HVSR: Fourier versus Response Spectrum and the First versus the Highest Peak Frequency

2020 ◽  
Vol 110 (2) ◽  
pp. 427-440 ◽  
Author(s):  
Chuanbin Zhu ◽  
Fabrice Cotton ◽  
Marco Pilz
Keyword(s):  
Site Response ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Spectral Ratio ◽  
Peak Frequency ◽  
Fourier Amplitude ◽  
Resonant Frequencies ◽  
Overall Performance ◽  
Fourier Amplitude Spectrum ◽  
Hvsr Technique

ABSTRACT In this investigation, we examine the uncertainties using the horizontal-to-vertical spectral ratio (HVSR) technique on earthquake recordings to detect site resonant frequencies at 207 KiK-net sites. Our results show that the scenario dependence of response (pseudospectral acceleration) spectral ratio could bias the estimates of resonant frequencies for sites having multiple significant peaks with comparable amplitudes. Thus, the Fourier amplitude spectrum (FAS) should be preferred in computing HVSR. For more than 80% of the investigated sites, the first peak (in the frequency domain) on the average HVSR curve over multiple sites coincides with the highest peak. However, for sites with multiple peaks, the highest peak frequency (fp) is less susceptible to the selection criteria of significant peaks and the extent of smoothing to spectrum than the first peak frequency (f0). Meanwhile, in comparison to the surface-to-borehole spectral ratio, f0 tends to underestimate the predominant frequency (at which the largest amplification occurs) more than fp. In addition, in terms of characterizing linear site response, fp shows a better overall performance than f0. Based on these findings, we thus recommend that seismic network operators provide fp on the average HVSRFAS curve as a priority, ideally together with the average HVSRFAS curve in site characterization.

Site response analysis of liquefiable soil employing continuous wavelet transform

2022 ◽  
Vol 12 (1) ◽  
pp. 1-33
Author(s):  
D. Chavan ◽  
T.G. Sitharam ◽  
P. Anbazhagan
Keyword(s):  
Wavelet Transform ◽  
Site Response ◽  
Amplitude Spectrum ◽  
Ground Surface ◽  
Time History ◽  
Response Analysis ◽  
Fourier Amplitude ◽  
Acceleration Time ◽  
Liquefiable Soil ◽  
Fourier Amplitude Spectrum

Propagation of the earthquake motion towards the ground surface alters both the acceleration and frequency content of the motion. Acceleration time record and Fourier amplitude spectrum of the motion reveal changes in the acceleration and frequency content. However, Fourier amplitude spectrum fails to give frequency-time variation. Wavelet transform overcomes this difficulty. In the present study, site response analysis of a liquefiable soil domain has been investigated employing wavelet transform. Three earthquake motions with distinct predominant frequencies are considered. It is revealed that the moment soil undergoes initial liquefaction, it causes a spike in the acceleration time history. Frequency of the spikes is found to be greater than the predominant frequency of the acceleration-time history recorded at the ground surface from the analysis. Interestingly, the spikes belong to the sharp tips of the shear stress-shear strain curve. Immediately after the spike, acceleration deamplification is observed. Post-liquefaction deamplification (filtering) of the frequency components is also observed.

Response spectrum-based seismic response of bridge embankments

2020 ◽  
Vol 57 (11) ◽  
pp. 1639-1651
Author(s):  
Juan-Carlos Carvajal ◽  
William D. Liam Finn ◽  
Carlos Estuardo Ventura
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Seismic Response ◽  
Response Spectrum ◽  
Damping Ratio ◽  
Stress Profile ◽  
Cyclic Shear ◽  
Equivalent Linear ◽  
Design Response Spectrum ◽  
Peak Shear Stress

A single degree of freedom model is presented for calculating the free-field seismic response of bridge embankments due to horizontal ground shaking using equivalent linear analysis and a design response spectrum. The shear wave velocity profile, base flexibility, 2D shape, and damping ratio of the embankment are accounted for in the model. A step-by-step procedure is presented for calculating the effective cyclic shear strain of the embankment, equivalent homogeneous shear modulus and damping ratio, fundamental period of vibration, peak crest acceleration, peak shear stress profile, peak shear strain profile, equivalent linear shear modulus profile, and peak relative displacement profile. Model calibration and verification of the proposed procedure is carried out with linear, equivalent linear, and nonlinear finite element analysis for embankments with fundamental periods of vibration between 0.1 and 1.0 s. The proposed model is simple, rational, and suitable for practical implementation using spreadsheets for a preliminary design phase of bridge embankments.

scholarly journals Bizarre Waveforms in Strong Motion Records

2015 ◽  
Vol 2015 ◽  
pp. 1-17
Author(s):  
Baofeng Zhou ◽  
Haiyun Wang ◽  
Lili Xie ◽  
Yanru Wang
Keyword(s):  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Time History ◽  
Strong Motion ◽  
Ratio Method ◽  
Asymmetric Waveform ◽  
Baseline Drift ◽  
Strong Motion Records ◽  
Before And After ◽  
Fourier Amplitude Spectrum

This paper collects a rich set of strong motion records in some typical earthquakes domestic and abroad, checks its seismic events, converts the data format, corrects the zeroline and draws the waveform. Four kinds of abnormal phenomena on the acceleration waveform are revealed, such as spike, asymmetric waveform, obvious baseline drift, and strong motion records packets separation. Then reasonable processing approaches are derived from the preliminary analysis of the generation mechanism for abnormal phenomena. In addition to the effects on time history, Fourier amplitude spectrum and response spectrum are studied before and after strong motion records correction. It is shown that (1) mechanism of spikes is rather complicated; however spikes can be eliminated by “jerk” method, ratio method, and the consistency of the three-component PGA time; (2) mechanism of the asymmetric waveform is of diversity; however, to some extent, the Butterworth low-pass filtering can be applied to correct it; (3) two pieces of strong motion record packets can be connected by searching continuous and repeated data; (4) the method of cumulative adding can be used to find the clear baseline drift; (5) the abnormal waveform directly affects the characteristics of time history and frequency spectrum.

Site Response Evaluation of Agartala City Using Geophysical and Geotechnical Data

2013 ◽  
Vol 4 (2) ◽  
pp. 53-73 ◽  
Author(s):  
Arjun Sil ◽  
T. G. Sitharam
Keyword(s):  
Ground Motion ◽  
City Planning ◽  
Site Response ◽  
Response Spectrum ◽  
Ground Surface ◽  
Disaster Mitigation ◽  
Site Class ◽  
Surface Level ◽  
Design Response Spectrum ◽  
The Mean

In this paper, the study addressed how the local geology and soil condition influences on incoming ground motion. Subsurface Geotechnical (SPT) and geophysical (MASW) data in 27 locations at Agartala city have been obtained and used to estimate the surface level response. The vulnerable seismic source (Sylhet fault) has been identified based on deterministic seismic hazard analysis (DSHA). The stochastic point source seismological model has been used to generate synthetic ground motion at 27 locations where MASW tests were conducted. The site response analyses have been performed using SHAKE2000.The results are presented in the form of contour maps in terms of PGA, amplification factor (AF) and spectral accelerations of periods (0.20sec, 1.0sec). The highest amplifications (2 to 3) were observed in the intermediate periods between 0.20 to 1.0sec ranges. However, the mean response spectrum has also been developed for both the rock and ground surface that has mean PGA 0.285g at rock and 0.35g at the surface. Further, the IS code and NEHRP provisions were compared with the mean surface level response spectrum. The IS code provision overestimates the mean response spectrum for all the periods except the periods from 0.26-0.42 sec. Based on the present study, the average shear wave velocity (Vs30=236±52 m/s) of Agartala actually falls a site class-D category (180 m/s <Vs30<360 m/s) as per NEHRP provisions and the design response spectrum has been developed. The developed site specific design response spectrum and other results would be very useful for city planners/designers and the Govt. for earthquake resistant design, city planning, also to identify vulnerable locations, structures suitability identification and also better disaster mitigation planning of the city area.

Near-Fault Baseline Correction Method and Appliction in Wenchuan Earthquake

2012 ◽  
Vol 166-169 ◽  
pp. 2517-2521
Author(s):  
Xiao Bo Peng ◽  
Xiao Jun Peng ◽  
Wei Lin Yang
Keyword(s):  
Wenchuan Earthquake ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Time History ◽  
Relative Displacement ◽  
Correction Method ◽  
Baseline Correction ◽  
Fourier Amplitude ◽  
Surface Rupture ◽  
Fourier Amplitude Spectrum

To eliminate the drifting in recordings from Ms8.0 Wenchuan earthquake, a modified two segments baseline correction method is brought up and systematic acceptance standard is presented. The method is applied to recordings from Qingping station and Bajiao station, which are closest stations to surface rupture traces. The effect of baseline correction on acceleration time history, Fourier amplitude spectrum and 5% damped relative displacement response spectrum is analyzed.

Comparison of Equivalent Linear and Nonlinear Site Response Analysis Results and Model to Estimate Maximum Shear Strain

2016 ◽  
Vol 32 (3) ◽  
pp. 1867-1887 ◽  
Author(s):  
Brian Carlton ◽  
Kohji Tokimatsu
Keyword(s):  
Shear Strain ◽  
Site Response ◽  
Response Spectrum ◽  
Peak Ground Velocity ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Ground Acceleration ◽  
Maximum Shear Strain ◽  
Nonlinear Site Response ◽  
Equivalent Linear

We compared the results of equivalent linear (ELA) and nonlinear site response analyses (NLA) and found that the differences between the values of the peak ground acceleration ( PGA), peak ground velocity ( PGV), Arias intensity ( I a), significant duration ( D5–75), and response spectrum for periods between 0.025 s and 2 s predicted by each method are non-negligible for maximum shear strain values predicted by ELA ( γ max, ELA) greater than 0.04% to 1.0%. As γ max, ELA increases, ELA in general predict smaller shear strain and D5–75 values, and larger PGA, PGV, I a, mean period, and response spectral values for periods less than 0.1 s and periods near the natural site period than NLA. To help researchers and practitioners decide when to use ELA and/or NLA, we developed a model to estimate γ max, ELA before conducting a site response analysis.

Regional attenuation models in Central and Eastern North America using the NGA-East database

2021 ◽  
pp. 875529302110187
Author(s):  
Jeff Bayless
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Gulf Coast ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Amplitude Spectrum ◽  
Active Regions ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

Selection of random vibration theory procedures for the NGA-East project and ground-motion modeling

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1420-1439
Author(s):  
Albert R Kottke ◽  
Norman A Abrahamson ◽  
David M Boore ◽  
Yousef Bozorgnia ◽  
Christine A Goulet ◽  
...  
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Random Vibration ◽  
Amplitude Spectrum ◽  
Motion Modeling ◽  
Peak Response ◽  
Vibration Theory ◽  
Random Vibration Theory ◽  
The Time Domain ◽  
The Impact

Traditional ground-motion models (GMMs) are used to compute pseudo-spectral acceleration (PSA) from future earthquakes and are generally developed by regression of PSA using a physics-based functional form. PSA is a relatively simple metric that correlates well with the response of several engineering systems and is a metric commonly used in engineering evaluations; however, characteristics of the PSA calculation make application of scaling factors dependent on the frequency content of the input motion, complicating the development and adaptability of GMMs. By comparison, Fourier amplitude spectrum (FAS) represents ground-motion amplitudes that are completely independent from the amplitudes at other frequencies, making them an attractive alternative for GMM development. Random vibration theory (RVT) predicts the peak response of motion in the time domain based on the FAS and a duration, and thus can be used to relate FAS to PSA. Using RVT to compute the expected peak response in the time domain for given FAS therefore presents a significant advantage that is gaining traction in the GMM field. This article provides recommended RVT procedures relevant to GMM development, which were developed for the Next Generation Attenuation (NGA)-East project. In addition, an orientation-independent FAS metric—called the effective amplitude spectrum (EAS)—is developed for use in conjunction with RVT to preserve the mean power of the corresponding two horizontal components considered in traditional PSA-based modeling (i.e., RotD50). The EAS uses a standardized smoothing approach to provide a practical representation of the FAS for ground-motion modeling, while minimizing the impact on the four RVT properties ( zeroth moment, [Formula: see text]; bandwidth parameter, [Formula: see text]; frequency of zero crossings, [Formula: see text]; and frequency of extrema, [Formula: see text]). Although the recommendations were originally developed for NGA-East, they and the methodology they are based on can be adapted to become portable to other GMM and engineering problems requiring the computation of PSA from FAS.

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